The purpose of the proposed research is to examine the importance of (1) intramolecular hydrogen bonding in maintaining a biologically significant conformation of oxytocin and (2) intermolecular hydrogen bonding of the asparagine and the glycinamide residues of oxytocin to its receptor in eliciting the characteristic biological activities. We propose to synthesize and biologically evaluate two analogs of oxytocin ---one to examine the importance of the hydrogen bond in the cyclic moiety of oxytocin as proposed in the 'biologically active' conformation on the basis of NMR studies, and the other to find out the contributions of all the three proposed intramolecular hydrogen bonds together. There is yet no acceptable explanation as to why most of the modifications of the asparagine and the glycinamide residues of oxytocin give analogs with negligible biological activities. We intend to synthesize and biologically evaluate a few selected analogs of oxytocin to determine if the C double bond O of the carboxamide groups of these two residues are critical for intermolecular hydrogen bonding with appropriate groups in the receptor. The results of the proposed research will constitute an analysis of the applicability of NMR data in designing hormone analogs with predictable biological activities and will give an insight into the mechanisms of hormone-receptor interaction.